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Earth from Space > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

Describe light as a wave

A

Light is electromagnetic radiation, consisting of an oscillating electric field and magnetic field (waves)

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2
Q

What is 3.0 x 10^8 m/s

A

The speed of light

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3
Q

What determines colour?

A

Wavelength

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4
Q

As the wavelength size becomes smaller (moves further right on the spectrum), does energy increase or decrease?

A

More energy is carried with a smaller wavelength (further on the spectrum)

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5
Q

What is a blackbody?

A

A theoretical object that that absorbs ALL radiation hitting it and is a perfect emitter of EM

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6
Q

What does Wien’s displacement tell us?

A

The Max wavelength of an object is inversely proportional to temperature: Smaller wavelengths have more energy and therefore are hotter (blue)

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7
Q

What does Wien’s law tell us about solar vs terrestrial radiation?

A

The peak of solar radiation is around 500 nm in the visible range, terrestrial radiation is in the infrared and therefore is not visible to us

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8
Q

Compare Active and Passive remote sensing

A

Active includes sensors that have their own energy (LIDAR)

Passive relies on energy from a different source like reflective from the sun

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9
Q

What are the two kinds of reflectance?

A

Specular or Mirror-like Reflectance (smooth surfaces)

Diffuse Reflection (rough surfaces)

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10
Q

Why does water show up black when using near-infrared in Landsat imagery?

A

Water’s spectral reflectance signature is only present in the Blue, Green, and Red part of the spectrum (absorbs other wavelengths)

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11
Q

Are real-world surfaces Lambertian?

A

No, most surfaces are non-Lambertian. They do not reflect light equally in all directions.

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12
Q

What is the Bidirectional Reflectance Function (BDRF)?

A

The consideration of the direction of incidence radiation as well as the viewing direction. The differences in angle change the amount of energy being detected.

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13
Q

When does a “hot spot” occur?

A

When the viewing angle is the same as the angle of the sun.

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14
Q

What phenomenon of BDRF is the result of specular reflection?

A

Sun Glint

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15
Q

When does atmospheric scattering occur?

A

Radiation is redirected out of the incident path but the wavelength of the scattered light doesn’t change.

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16
Q

How do O2, N2, water vapour, and other molecules or aerosols affect light?

A

They scatter light into the path of sensors or away from the sensors

17
Q

Which particle size is associated with Rayleigh scattering?

A

smaller than wavelength (ex. gas molecule) = blue/violet part of spectrum

18
Q

What is Mie Scattering?

A

When the size of the particle is about the same size of the wavelength (ex. smoke or dust) = red & orange part of spectrum

19
Q

If the particle is much larger than the wavelength what occurs?

A

Non-selective scattering (ex. water vapour) = no strong colour as all equally scattered

20
Q

Why can you still see details in a picture of a shadow?

A

Scattering of light into sensor path

21
Q

What are transmission and transmittance?

A

The passing of light through a medium

The proportion of light allowed to pass through the medium

22
Q

What happens when light is absorbed by a material?

A

It can be converted to other forms of energy (ie. thermal) = no longer available to sensors

23
Q

How can we use absorption to determine what is in the atmosphere?

A

We can analyze absorption bands at specific wavelengths to see what is doing the absorbing

24
Q

How is fluorescence different from absorption?

A

Causes excitation of an e- to elevate it to a higher energy level, when it drops to steady-state it emits EM

25
Q

How can we apply fluorescence in remote sensing?

A

Greater amounts of chlorophyll relate to higher fluorescence which can help to monitor photosynthetic activity and therefore carbon sequestration

26
Q

what is a forward model?

A

simulates light returned to a sensor given known properties of the atmosphere and earth’s surface

27
Q

What is an inversion model?

A

Determine properties of atmosphere or earth’s surface given a known reflected signal

Earth from Space (9 decks)

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